Infection acquired from health care environments is one of the leading major medical complications in the present world. Studies have shown that almost 6% of patients admitted to hospitals acquire infections and the number of such cases is increasing. According to reports by the US Center of Disease Control that hospital acquired infections account for more than 2 million cases leading to 99,000 deaths annually.
The most common hospital acquired infections include urinary tract infections, surgical wound infections and those associated with intravascular cannulas. The mode of transmission of these infections is mostly by physical contact with infected medical devices. Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli are the most common bacterial isolates that give rise to these infectious diseases. It has been observed that most of the bacterial strains develop resistance to antibiotics over a period of time. In the hospital environment, over 50% of Staphylococcus aureus have developed resistance to methicillin, which ultimately leads to surgical wound infection and catheter related sepsis. Some of the emerging antibiotic resistant pathogens include vancomycin resistant enterococci, vancomycin intermediate staphylococcus, and multiple antibiotic resistant Gram negative organisms like acinetobacter, enterobacter and mycobacterium. 
Biocidal polymers offer promise in helping curb the spread of infections by providing coatings for applications such as biomedical devices or molded articles. An antimicrobial avoids adhesion and proliferation of planktonic microbes on the surface by either repelling or killing the microbes. While repelling surfaces can be achieved by creating ultrahydrophobic surfaces, the killing of microbes can be achieved by either biocide release or contact kill. In some instances release and contact kill are combined. Contact antimicrobial function is accomplished by covalently bonding the biocide; thereby, promising durability. Because contact kill precludes the biocide entering the bacterial metabolic processes, elimination of bacterial resistance buildup may result. Interest in contact kill has led to a number of studies on polymers with covalently bound alkylammonium groups.
Contact kill silicone coatings include a class of biocidal polysiloxanes with 3-(alkyldimethylammonium)propyl pendant groups. Antimicrobial activity of PDMS chains terminated with quaternary ammonium functionalities bearing oxyethylene moieties has been studied. In a humid environment, these oxyethylene chains spread out, exposing the ammonium moieties which imparts biocidal property to these compounds. Simultaneously, cationic silicones have also been used as surface modifiers, one of them being a reactive silane, (MeO)3Si(CH2)3N+Me2C18H37Cl− (DC 5700). This compound, developed by Dow Corning, renders bactericidal properties to surfaces like glass, cotton, polyester fibers.
Quaternary function (sometimes referred to herein as “quat”) has been introduced into PDMS coatings using RquatSi(OR)3 and condensation cure. With trifunctional RquatSi(OR)3 competition must occur between quaternary function in the bulk (crosslinker) and at the surface. Accordingly, 10-15 weight percent RquatSi(OR)3 was required to obtain modest antimicrobial activity, which is undesirable due to expense.
Cationic surface active polyurethane surface modifiers as antimicrobial coatings have been previously studied. Examples include HMDI-BD based polyurethanes such as shown in FIG. 1 as the polymer surface modifier containing a random P[AB] copolyoxetane soft block, where A is a fluorine based oxetane (3FOx) and B contains a quaternary ammonium side chain (C12) with a twelve membered carbon chain. HMDI is H12MDI, (4,4′-(methylene bis-(p-cyclohexyl isocyanate)) and BD is 1,4-butane diol have been used for hard blocks in studies for antimicrobial coatings.
A small percentage of this modifier polyurethane was blended with a HMDI-BD-PTMO polyurethane (base polyurethane) which is commonly used in various industrial applications. It was observed that the resulting P[AB] polyurethane, when blended with an HMDI-BD-PTMO polyurethane, exhibited excellent antimicrobial properties. However, the surface active charge was not stable, and the antimicrobial property decreased drastically after two weeks.
Betaines are a specialized family of zwitterion that comprise both a cationic moiety and anionic functional groups. Various betaines have shown good antibacterial activity and a broad scope of inhibition. In previous studies, betaines were introduced into to the polymer backbone through ether, amide, imide, or other hydrolysable chemical bonds. However, these suffered from leaching from the substrate and decreasing antibacterial activity during use. The antibacterial agent siloxanesulfopropylbetaine (SSPB) with a reactive alkoxysilane group for the finishing of cotton textiles has been previously studied.